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%I #18 Jul 20 2013 02:39:41
%S 1,2,4,3,6,12,5,10,20,7,14,28,9,18,36,11,22,44,13,26,52,15,30,60,17,
%T 34,68,19,38,76,21,42,84,23,46,92,25,50,100,27,54,108,29,58,116,31,62,
%U 124,33,66,132,35,70,140,37,74,148
%N Irregular triangle which lists the three positions of 2*n-1 in A060819 in row n.
%C There are no multiples of 8 in the triangle.
%C A047592 contains a sorted list of all elements of the triangle.
%C The triangle is a member of a family of triangles with parameter k that list the k positions of 2*n-1: 2*n-1 in A000027 (k=1), A043547 the k=2 positions in A026741, the triangle 1,2,4,8; 3,6,12,24;... with the k=4 positions in A106609, or the triangle 1,2,4,8,16; 3,6,12,24,48;... with the k=5 positions in A106617.
%H Vincenzo Librandi, <a href="/A225055/b225055.txt">Table of n, a(n) for n = 1..1000</a>
%F T(n,1) = 2*n-1. T(n,2) = 4*n-2. T(n,3) = 8*n-4.
%e 1, 2, 4; # 1 at A060819(1), A060819(2) and A060819(4)
%e 3, 6, 12; # 3 at A060819(3), A060819(6) and A060819(12)
%e 5, 10, 20;
%e 7, 14, 28;
%e 9, 18, 36;
%e 11, 22, 44;
%e 13, 26, 52;
%e 15, 30, 60;
%t numberOfTriplets = 19; A060819 = Table[n/GCD[n, 4], {n, 1, 8*numberOfTriplets}]; Table[Position[A060819, 2*n-1], {n, 1, numberOfTriplets}] // Flatten (* _Jean-François Alcover_, Apr 30 2013 *)
%Y Cf. A147587. A042968.
%K nonn,tabf,easy
%O 1,2
%A _Paul Curtz_, Apr 26 2013
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